A 16-year-old boy who stabbed a man with a machete in Stevenage town centre narrowly avoided puncturing his heart.

The blade thrust missed the victim’s heart by just five millimetres and almost killed him, St Albans Crown Court heard.

The attacker, from Stevenage – who cannot be identified for legal reasons – stabbed the man after they had an argument in Swingate in the town on the afternoon of January 5.

Judge Andrew Bright QC sentenced him to three-and-a-half years in a detention centre, after hearing the boy’s mum had done all she could to steer him away from a culture of gangs, knives and drugs by moving the family to Stevenage from south London.

But, despite her best efforts, her son had chalked up a bad record of offending – including six previous convictions for having an offensive weapon or knife.

The court was told that the 36-year-old victim and the boy were involved in an altercation in Swingate.

The victim had turned to make his way back towards his car, and had his back to the boy – who then produced the machete and stabbed him through the chest.

The victim didn’t realise he had been badly wounded, and tried to run away – but ran out of breath and began sweating heavily. He then became aware of a wet patch on his back, and realised he had been stabbed.

Police attended and the boy was picked up nearby. He was found to have blood on his hands.

An ambulance and fast response vehicle arrived, but an air ambualance was required to airlift the victim to Addenbrooke’s Hospital in Cambridge.

Judge Bright was told the machete was never found.

In court, the boy pleaded guilty to wounding with intent and having a bladed article with a blade or point.

Judge Bright told the court he was full admiration for the defendant’s mother – but that in spite of the move out of London to Hertfordshire, the boy’s behaviour hadn’t significantly improved.

The judge said: “You could so easily have been facing a charge of murder. It’s only good fortune that saved him from a bloody death.”